They are here. As with anything, content is the issue. In fact some manufacturers have already made and stopped producing them, as the market didn’t exist. They are aimed mostly at digital signage or custom visualization content right now.
There are a couple types-
Stereoscopic or flat 3D( if that makes sense) left and right eye layers. Limited viewing angle and reduced resolution.
These folks have the displays and help with content
Light Field- These have several elements behind EACH pixel that push light out at different horizontal angles. Because they work this way, moving your head, will allow you to see different colors from the SAME pixels. Someone standing to the left can see behind an object to the right. Where someone standing at center cannot.
These do not have any “vertical” separation yet, meaning there are not different pixels viewable from below, as there are from above. But left to right these give you a truer 3D effect.
See this for a diagram
and this for product (notice the camera travels left, showing the white gear behind the blue one, etc.)
If you have 2:52 to spare, this gives a quick and dirty overview of 3D vs holographic and the steps in between. The product above is featured at 2:04.
Best and God Bless,